This invention relates to a method of plasma vapour deposition of metal into a recess in a workpiece in a manner to achieve re-sputtering of the metal at the base of the recess onto the sidewalls.
It is known to use ionised metal sputtering techniques involving a high powered unbalanced magnetron discharge source. The metal ions are attracted to the base of a recess formed in a workpiece, such as a semi-conductor wafer, using a DC bias induced by applying RF power to the wafer pedestal. This gives an improved bottom and sidewall coverage in the recess. Further improvement is known to be achievable by re-sputtering the metal already deposited in the base onto the lower and mid parts of the recess sidewall. To achieve re-sputtering DC bias voltages in the range of 50 to 500 volts are required. The higher the DC bias the greater re-sputtering and there is an improvement in the sidewall coverage.
Even so the current results are not satisfactory for all purposes.